Integrated circuit memory devices, including integrated circuits incorporating both memory and logic, often include a redundancy circuit to replace defective memory cells. The redundancy circuit generally includes redundancy memory cells and redundancy fuse boxes. The redundancy memory cells replace the defective memory cells. The redundancy fuse boxes recognize the addresses of the defective memory cells when they are input, and generate a redundancy enable signal for driving the redundancy memory cells.
FIG. 1 is a block diagram of a memory device having a conventional column redundancy scheme. For clarity, only blocks associated with column redundancy are shown.
Referring to FIG. 1, the device having a conventional column redundancy scheme includes a plurality of memory blocks 101 and 103 having memory cells, a plurality of normal column selection line drivers 109 and 111 for driving the respective column selection lines (CSLn0) and (CSLn1) of the memory blocks 101 and 103, a plurality of redundant column selection line drivers 105 and 107 for driving the respective redundant column selection lines (RCSL0) and (RCSL1) of the memory blocks 101 and 103, and a plurality of column redundancy fuse boxes 113 and 115 respectively connected to the redundant column selection line drivers 105 and 107.
The column redundancy fuse boxes 113 and 115 pre-store the addresses of defective memory cells when defective memory cells exist in the corresponding memory blocks 101 and 103. Accordingly, the respective column redundancy fuse boxes 113 and 115 activate the corresponding redundant column selection line drivers 105 and 107 in response to an input column address (CA).
FIG. 2 is a circuit diagram of the normal column selection line driver shown in FIG. 1. FIG. 3 is a circuit diagram of the redundant column selection line driver shown in FIG. 1. Referring to FIGS. 2 and 3, a fuse (F21) is included only in the normal column selection line driver.
In memory devices having the conventional column redundancy scheme, one column redundancy fuse box generally is allocated to one redundant column selection line, so that the devices generally include column redundancy fuse boxes corresponding to the number of redundant column selection lines. However, the column redundancy fuse box generally has a large layout area, and a fuse portion generally must be accessible to be cut by a laser. Therefore, when the number of fuse boxes increases, the area of the chip generally becomes larger.